The present invention relates to a technical field of a control system of an engine in which a purge gas containing evaporated fuel desorbed from a canister is supplied to an intake passage.
Conventionally, arts are known, in which during a deceleration fuel cutoff of the engine, when it is determined that evaporated fuel easily overflows from a canister, the purge gas containing the evaporated fuel desorbed from the canister is supplied to an intake passage of an engine. For example, JP2007-198210A discloses such an art. By supplying the purge gas to the intake passage during the deceleration fuel cutoff as above, the overflow of the evaporated fuel from the canister can be reduced. Although the evaporated fuel within the purge gas supplied to the intake passage is discharged unburned to an exhaust passage through the engine, the unburned evaporated fuel can be purified by an exhaust emission control catalyst provided in the exhaust passage.
Further, in JP2007-198210A, when a temperature of the exhaust emission control catalyst is detected and the detected result indicates a temperature below a predetermined value, the supply of the purge gas to the intake passage is reduced to suppress degradation of emission performance.
However, in JP2007-198210A, even when the purge gas is supplied to the intake passage when the temperature of the exhaust emission control catalyst is the predetermined value or higher, depending on the temperature of the exhaust emission control catalyst, if an excessive amount of unburned evaporated fuel reaches the exhaust emission control catalyst, the emission performance may still degrade, which leaves room for improvement.